Process for the reactivation of contact catalysts



April 18, 1944. L A, GUYER PROCESS FOR THE REACTIVATION OF CONTACTCATALYSTS Filed April 14, 1941 2 Sheets-Sheet l INVENTOR JESSE AA GUYE'R5% TORNEY BY M -PY '18, 1944- J. A. GUYER 2,346,750

PROCESS FOR THE REACTIVATION OF CONTACT CATALYSTS JESSE A GUYER TTORNEYPatented` Apr. 1.8, 1944 iTE'D STATE;

am* .orma- PROESS FOR THE llEAC'.IEVJEION OF CONTACT CATALYSTS Jesse A.Guyer, Bartlesville, 0., assignor toA -Phillips Petroleum Company, acorporation of Delaware implication April 14, 1941, sensi No. 388,535 4ciaims. (ci. 19e-52) This invention relates to the catalytic treatmentof hydrocarbons over contact catalyst- `masses to promote conversionscommonly classied -as cracking, reforming, dehydrogenation, cyclization,desulfurization;isomerization and the like. More particularly, thisinvention relates to an improved method and process for the reactivationof catalyst masses employed in said conversions and which are more or`less progressively inactivated by the deposition of carbon and/or.

carbon-containing material on the catalyst particles. i

In catalytic conversions of the ltype indicated,

the nature of the reactants andthe conditions of` treatment are suchthat carbonaceous materials are formed and deposited on the catalystmass, l

thereby impairing the catalyst activity. While the amount ofcarbonaceous material deposited may vary with the hydrocarbonstockundergoing conversion, the original activity of the catalyst, and theconditions, particulagly the temperature of treatment, the ultimateresult is a decrease in conversion to an economically unsatisfactorylevel. From the standpoint of product, quality and yield, it becomesnecessary to reactivate the catalyst at suitable intervalsIcorresponding to some pre'- determined standard or average value ofeconomically satisfactory conversion. i i

In catalytic conversion processes wherein re activation of the'catalystat relatively'frequent intervals is necessary, it is common practice toincorporate into the plant design and equipment a sufcient number ofcatalyst-containing chambers so that a regular cycle of converting andreactivating. operations is possible. ordinarily includes a treatingperiod during which a unit .volume of the catalyst is employed in theconversion anda reactivating period during which the said unit volume-ofcatalyst is subjected in situ to controlled combustion conditions by thepassage of an oxygen-containing gas at or above the ignition temperatureof the carbonaceous deposits.

Reactiyation of solid granular catalyst masses by combustion requirescareful control of the rate of burning to prevent deterioration of thephysical and catalytic properties thereof by excessive temperatures. I-Ieatl transfer within vthe catalyst mass is poor due to thenon-conducting vnature of the particles, and temperature control during`combustion is usually attempted by the regulationl 'of the oxygencontent of the combustion atmostphere passedthrough the catalyst mass tothereinr limit the exothermic heatgenerated. Inl this manner thecombustion atmosphere may serve as- Such a cycleA both the .temperaturecontrol mechanism and the principal heat transfer medium. n

The heat of combustion is primarily a measure of the amount of`carbonaceous material burned, or in other terms, o f Vthe amount ofoxygen admitted to the catalyst, and reactivation is ordinarilydescribed as carried out in an atmosphere of relatively low oxygencontent. The rate Aoi' combustion is thus to be limited and theexothermlc heat to be controlled by the available oxygen in a unitvolume of the combustion atmosphere. Also, during the periodoireactivation it is often desirable to increase the oxygen concentrationof the combustion atmosphere as the carbon content of the catalystdecreases to maintain a reasonably constant temperature and 'speed thereactivation operation.

v However, the tremendous operating diicultes in such a procedure arecentered in the regulation of the oxygen content oi the combustionatmosphere. The oxygen content-must be maintained at very low valueswhich may be varied-Within known low limits during the reactivationperiod,

and this degree'oi regulationhas complicated the analytical and controlprocedures of the proposed reactivation processesin many cases to thepoint of inoperability. No ordinarily available gases have an oxygencontent in the range required during the initial stages of reactivation.Thus,

a source of .substantially oxygen-free gas. Such recycle gas may then beblended with oxygencontaining gas in producing a combustion atmosphereof controlled oxygen content.- This procedure is complicated by the factthat this recycle gas'may have a substantial and iiuctuating oxygencontent at variousintervals throughoutthe combustion period. Especiallyin the reactivation of catalysts disposed in multiple-tube reactors, th'combustion may proceed unevenly due to unequ l pressure drops in thevarious tubes so that the eiiluent gases from some tubes may containI,substantially the original concentration of equipment.

oxygen while that from otherv tubes may be oxygen-free. Similarly, incatalyst vessels of relatively'large. cross-sectional area unevencombustion may result from uneven carbon deposition. This fact in turnrequires a. constant and accurate determination of the oxygen content ofsaid recycle gas as long as it is being mixed withadditionaloxygen-containing gasahead of the catalyst chamber. Suchanalysis is difficult to make, and the necessary continualre-proportioning oi the gas streams being mixed introduces 'expensiveand troublesome operating control. In addition to these difficulties,the recycle gas stream contains corrosive compounds such ashydrogenfsulde and sulfur dioxide and abrasive constituents such as dustwhich aredestructive to compressors, blowers, controlinstruments andvarious other parts of the equipment of the system.

Thus, prior to recyclingthe euentcombustion gas from the catalyst beingreactivated is ordinarily chemically treated and/or scrubbed, dried,reheatedl and the like to remove components deleterious to the catalystor to the reactivating A iinal disadvantage is the high carbon monoxidecontent of said recycledl gases which, as hereinafter explained, is notdesirable in the combustion atmosphere.

It has also been proposed to supply the required substantiallyoxygen-free gas in the form of steam. Such proposals are not feasible inmany cases due to the high cost of providing the large amounts of steamrequired as well as to the frequent deleteriou eiects of highconcentrations of steam on t c catalyst. In the latter instance, controlof the'steam content as well as ci' the oxygen content' of thecombustion atmosphere leads to the multiplication of control problemsand to the use of expensive cooling and rev heating procedures to removeexcess steam by condensation and to reheat the combustion atmosphere toignition temperatures.

I have now discovered a method of conducting the reactivation ofcatalyst masses 4which from the standpoint of simplicity and economy ofop eration as well as the utilization 91 various novel` featureshereinafter described represents an important improvement in the art. Myinvention as exemplified in the control of the reactivation equipmentandl process has for its objects'the (elimination fof the disadvantagesformerly associated with catalyst reactivation by controlled combustion,and the employment ci' novel operating features and economics.

, I have found that the removal of carbonaceous material from a catalystmass vmay* be expedited and more easily controlled by the use of a com:bustion atmosphere` prepared by mixing an oxy-l gen-containing gas witha substantially oxygen- .free gas furnished from an external'supply ofsubstantially unvarying composition. I have iurther`discovered a novelmethod of producing said substantially oxygen-ree gas in any requiredvolume and at a temperature level which makes its generation and 'useinexpensive and 'easily controlled. With this constant supply ofsubstantially oxygen-free gas, I am able to control the reactivationprocess in all'stages o1' combustion with'ease and simplicity ofequipment heretofore impossible. Other advantages of my process such asfuel economy and utilization of waste heat togenerate' steam and powerfor the process will be obvious from' the following description.

I have noted that greatly improved results are obtained in reactivationbyI the use of a combustion atmosphere containing, in addition to aregassettovl 1) o+o2 oo2 (+174,6oo B. t. u.) m (2) C+CIO2 2C0 (-70,200B. t. u.)

When water lis formed yor is present in the combustion atmosphereadditional reactions are possible, as follows:

`Equationl'(1) represents the basic combustion re- I action which issubstantially instantaneous and 2m is yresponsible for e'xothermic heatduring reactivation. Equations (2) and (4) represent reacactions 'whichremove carbon from the catalyst y and at the same time absorb heat.Equations (3) and (5) represent reactions which may be disregarded atthe, temperature levels of 600 to i500u F. ordinarily employedinreactivation.

Reactions (2) and (4) are highly desirable in that they are endothermicand promote reactivation.. fI'o the extent that these reactions occur,.reactivation is expedited, andthe heat evolved by Reaction (1) ispartly absorbed. Both eilects are beneilciaLand the latter even permitsa slightly higher oxygen concentration in the combustion atmosphere. Ihave establishedithe fact that Re- 35 action (2) utilizing carbondioxide is of far greater signicance in this respect than Reaction (4)utilizing steam due to a greater reaction velocity at theabove-mentioned temperature levels. Thus, carbon dioxide is superior tosteam as a secondary reaction agent in the combustion atmosphere whilethe function of carbon monoxide as a product of the secondary reactionsis to suppress the said desirable reactions. For these reasons I preferto utilize a combustion atmos- 5 phere of closely controlled oxygencontent prepared by mixing an oxygen-containing gaswith a substantiallyoxygen-free' gas also containing maximumlquantities of carbon dioxideand minimum quantities of carbon monoxide. The concentration of steaminv said combustion atmosphere 'may not exceed-that present in ordinaryflue or stack gases and may be limited to values consistent withoperating economy and the susceptibility of the catalyst towarddeterioration .of steam.. 4

In one specific embodiment, my process comprises the steps of (1)preparing a substantially oxygen-free gas by the combustion of fuel gasunder moderate pressure in an atmosphere of m oxygen-containing stack orspent combustion gases; (2) lpurging. the catalyst space withsubstantially oxygen-freezes; (3) mixing the substantially oxygen-freegas with the stack gases or air to produce a mixture of limited oxygenconlcentration which is passed at suitable tempera- .l tures over thecatalyst to be reactivated; (4) increasing the oxygen content of thecombustion atmosphere as the reactivation proceeds to eiectivelymaintain the rate of combustion; and (5) utilizing the sensible heat ofthe eiiluent' gases -from the catalyst v4chamber and of variable volumesof the excess 'gas produced by step (1) to lgenerate steam and power forthe operation' of the process.

The `various operations outlined maybe illusintegrated.

' essere@ trated by the ow diagrams of Figures l and 2 v which showschematically two arrangements of equipment for the practice of myinvention.

With reference to Figure l, gas from stacE I.

which may be part of a heater or furnace em- -ployed in the catalyticprocess is withdrawn through cooler 2 and line 3 to steam-drivencompressor 4. The, compressor delivers the Agas through line 5 topressure combustion chamber 6.

' In chamber t lthe stack gas is mixed with suicint fuel gas from line'I to produce combustion products substantially free of oxygen. The gasstream leaving chamber 6 is divided, passing through line il to line I lwhich leads to the cata/- lyst chambers i2, I3 and through thebackpressure regulator 8 to the waste heat boiler Il. The `substantiallyoxygen-tree. gas` passing through line lll 'is thus available for usesrequiring, an inert atmosphere or for mixing with oxygen-containinglgas. The latter may be stack gas from line id or in some cases air fromline I5. The gases are introduced to the' catalyst chambers throughli'nes I6, I1 and i8.

The catalyst chambers are represented by two vessels although the numberis not restricted and will vary according to the conversion beingcnducted. These vessels are fitted with inlet manlfold` lines 50 and 5Iand outlet manifold lines 52 and 53 and vapor-inlet line 54 and vaporoutlet line 55 `for the passage of hydrocarbons undergoing conversion,and also valves as shown for switching the'ilow othydrocarbons andreactivat'ing gases from oneto, the other of the vessels. The catalystsmay bedisposed in a single bed or in sections on trays vand 'the like,or in multiple tubes of relativelyy narrow cross section. The cycle ofoperations may be illustrated with two vessels although in actualoperation with -more vessels the time' intervals ci the various `tion,reactivation is commenced by passing through chamber I3 a mixture ofoxygen-containing stack gasirom line Il and substantial-` ly oxygen-freegas, from line I0. The proportions of the mixture are regulated toproduce the desired oxygen content. Assumingthat a constant volume oi'gas is generated in combustion chamber t, the requisite volume isdelivered through line lil by, reduction of the ilow through theback-pressure regulator 9. Theeiliuent gas from chamber i3 passesthrough lines 2B, 2l and 2c to the waste heat boiler i I. I The gas'stream leaving the boiler consists of the combined ystreams entering.b'ylines fand 2l, and passesthrough line 25 to vent 26. 'f The-steamgenerated in the boiler II is withdrawn from the accumulator 21 throughthe pipe 2u and superheated in the heat exchanger 29 by heat exchangewith the hotl gases from pipe it. The superheated steam is 'supplied tothe prime mover il@ through the pipe 3l. Steam from an external sourcemaybe admitted to thev prime mover from the pipe t2 and used to augmentVthe .-f v4from the waste heat boiler. The cond ate from the prima mover30 passes through trap tu and line 34 top'ump Il which returns thelcondensate through line 38. yPart of the water passing through line 36is sent to boiler l I as feed water through line 31 together withmake-up waterirom line 38. 'Water is also injected into the-combustionchamber '8 through line 39 for the purpose of cooling the combustion sasproduced. Additional cli'ng of the gas passing through line It isobtained by water injection through line Il and heat exchange in theheat exchanger 29.

The excess steam required over that produced l in the waste heat boilermay be supplied from an external source as indicated, or maybe producedwholly within the system by the .supplemehtary combustion of fuel inboiler il by means of auxiliary burnersnot shown. These latter may alsobe useful in starting up the plant illustrated before waste heat fromthe gasj streams is avail able.

As the reactivation proceeds, the oxygen concentration of thereactivating combustion atmosphere may be increased, and largerproportions of stack gas introduced through line le. In fact,

Aafter the major portion of `the carbonaceous residue on the catalysthas been oxidized, undiluted stack gaslmay'be used, or still higheroxygen concentrations may be obtained -by the introduction of airthrough line I5. In these latter stages, the temperature of thecombustion atmosphere may bemaintained at the desired levels byrelatively small volumes'of hot gases from line it.l When 4reactivationis complete, the catalyst chamber is again purged with substantiallyoxygen-free sas byclosing lines it and. I5 and passing only the streamfrom line l0 at the pro'rfertemperature. Thereafter the catalyst isready tolte placed in conversion service.

Figure 2 shows a modieation of the apparatus in which the waste heatboiler is placed adjacent to or integral with the combustion chamber.rZin this fashion, the injection or water or` steam to lower thetemperature of the gas generated in said combustion chambermay bereduced or eliminated. The stack gas Withdrawn from stack l passesthrough cooler 2 and line 3 to compressor y t. From thecorhpressor thegas passes through line 5 to the combined combustion chamber and boilerunit di wherein combustior'with fuel'from ine l is conducted to producethe substantially oxygen-free gas. `Gaseous products of combustion passthrough one tube. bank of the boiler, which' is divided by apartition42, and the oxygen-free gasV cooled by passage through the boiler tubesthen passes'to line I0.

Again'considering the catalyst in chamber I3 -to' be undergoingreactivation, the catalyst bed is iirst purged of volatile hydrocarbonsby means of.`

substantially xygen-free gas'passlng from the combustion c amber "ofunit el and through lines lil, i6, and I8 into chamber i3. The purgedmaterial exists through ,lines 2li, 26, and 2E..

The reactivat'lng combustion lis then commenced by passage of a'mixtureof substantially oxygen-free gas and oxygenl-co'ntaln'ing stack gas fromlines I0 and. I4. The temperature ofthe' mixture is 'controlled by. thevolume of hot gas entering by line I0, and the oxygen content isregulated by the volume of vstack gas from line lli. Any excess of gasin line It above that required ior the mixture is vented through back--ypressure regulator Q to line 25 and vent'gt. The

eihuent gas from chamber Iii passes through lines unit 5H, and thencethrough line 25 to vent 2t.'

The steam generated in the unit di is taken from accumulator 2 throughlines 28 and 3l to the prime mover 30. Steam from' an external sourcemay be supplied through line 32. The condensate from the compressorengine is taken through trap 33, line 34 and pu'mp 35, and re turned totheunit lil through heat exchanger lll and line 36. Exchanger M servesas a feed Water preheater and removes part pf the heat added to thestack gas stream by the compression step. Boiler feed water from line 36is passed to the unit il through line 3l together with maire-up waterfrom line 38. Water from line 36 may -be injected through line 39 intothe combustion chamber of the unit il if desired, although in most casesthe necessary reduction in the temperature of the gas is accomplished inthe boiler tubes. f o

Combustion of fuel in an atmosphere of stack gas is carried out incombustion chamber d and in unitil il at moderate superatmospheric pres-'H without further ceung.- The gas stream sures 01515-50 pounds gauge orsuicient' to mainv tain iiow ofthe combustion. atmosphere withoutfurther compression. The pressure of combus tion may be only slightlybelow the discharge pressure of. the compressor which delivers theoxygen-containing stack gas to both the combustion chamber and the gasmixing lines ahead cf the catalyst chambers. This condition con formswith equalization of pressure in the mixing operation anchthe use of thecompressor to ,flow the combustion atmosphere through'both thecombustion chamber and the catalyst chan/mers.

The system pressure from the compressor discharge to the outlet of thewaste-heat boiler may be regulated Within the indicated pressure rangeby suitable back-pressure regulators.

The combustion of fuel gas in'an atmosphere of stack gas having anoxygen content lower than air and usually between 5 and 10 volume percentl vrpassing through line I0 may be further cooled by additionalwater'injected through 'line 40 prior to lpassage over the catalystbeing reactivated. In every case the degree of 'cooling of the gas inline I0 willbe governed by the relative proportions of said gas used inthe mixture with stack gas from line I4 and by the desired temperatureof the said mixture at the inlet of the catalyst chamber.

Instead of cooling the gas passed into the catalyst `chambers I2, i3vand comprising the substantially oxygen-free gas issuing from chamberil or unit 4|, by the injection of liquid water through line' 39, by theinjection of liquidjwater through line 40, or by heat exchangeindexchanger 29 with the steam issuing from accumulator 2l, this gasmaybe cooled by the direct addition thereto of water in the form of steam.'The cooling steam may conveniently be made by the injection of steam assuch before or after the blending with air or with stack gas.

The stack gas which serves as the combustion medium in chamber 6 and asthe source of oxygen-containing gas in, the. combustion atmos-v phere iscooled to a temperature of about 100 to 300 F. 'ahead of the blower 4,The temperature rise, due to compression may be oiset by a heatexchanger inthe blower discharge and the heat extracted-may be utilizedin any desired manner,

for example; to pre eat the feed water to the boiler asin the mod cationoflFigure 2. The

` compressor output is regulated according to the produces asubstantially oxygenffree gas oi? high y carbon dioxide content attemperatures which are markedly lower than those resulting from 'thecombustion of fuel gas in air.. Thus with stack gases containing about10Y volume per cent of onygen, the combustion temperature in chamber t3is about 2400" F., whereas if air were used the temu perature would bein the range of 32003500 F. This lowering of the temperature in chamber@is reflected in savings in the cost of construction and maintenance ofchamber` t, because the higher temperatures cause more rapidVdeterioration of the shell, yrefractory linings,'checkerwork partitionsand effluent gas lines.

The lower temperature of the gas generated -in the pressure combustionchamber is also benecial in the reduction of the degree of' coolingwhich must be done to produce Itemperatures compatible with the various'reactivation' steps. For example, when it is desired to lower thetemperature of the gas leaving chamber Bt about 1400* F., the generationof said gas at 2400 'F'. instead of 3200 F. results in a reduction ofabout 50 per cent in the weight of steam required for the temperaturereduction. When water isomployed there is a corresponding reduction inthe amount required. The temperature reduction at the outlet of chamber6 may bev done in two sta-gesl if A desired. Thus water may beinjecteddirectly into the chamberthroush line 39to reduce the gastemperaturesulciently to protect the line 8 and the portion of the gaspassing through regulator 9 may be conducted to boilergas' requirementsof-the various phases of reactivation, with a constant volume ordinarilybeing supplied to' the combustion4 chamber 6 or unit 6|. The' amount offuel introduced is adjusted to the oxygen content of the stack gas. andthe gas passing ,tov pipev I0; is substantially oxygen-free when thefuel added requires about per cent or more of the oxygen present forcombustion. In this type of operation a constant supply of substantiallyoxygen-free gas .is available at all'times without the'necessity of anyregulation to compensate for other variations throughout the system.Whatever excess of said substantially oxygen-free gas is produced isutilized in the production of steam.

The. basic control of myoprocess is reduced to the proportioning of thegas streams which are mixed to prepare the combustion atmosphere. 'Inits simplest aspects, the controlcomprises regulation-o1 the valvesorflowcontrollers in the lines I0, i4, and I5 to produce a gas mixtureof any desired oxygen concentration 4up to the maximum represented bythe stack gases. Beyond this maximum,v air may be'used to produce anydesired oxygen concentration upto the oxygen content of air. Theseranges cover all ordinary re= activatinsteps and indicate theflexibility and simplicity of operation of my process. Simple operatingcontrols' such as proportioning ilow controllers actuated by thetemperature of the eiiiuent gas from the catalyst bed lmay be employedif desired.'

IIfhe initial purge of the catalyst bedprior to reactivation isaccomplished. by discontinuing the flow o1' hydrocarbons, releasing the,pressure on the vessel, and .introducing substantially oxygen-:free gaswith or without added steam at a temperature usually approximating that.em-

ployed during conversion. In' some instances of treating very heavymaterial, subatmospheric pressures may be use'd to expedite removal ofhydrocarbons.' While the purge gas may be asiatico mixtures ofsubstantially oxygen-free gas with steam, I often prefer to minimizevthequantities of steam used on account of possible reactions occurringbetween the catalyst and steam which cause loss of catalytic activity.

A-Iterthe catalyst bed is purged substantially free of volatilehydrocarbons, combustion is initiated by the introduction oi gascontaining low percentages of oxygenj The temperature of the catalystmaybe raised or lowered'by the purging operation, and the temperature' ofte cm1-4 gen-containing combustion atmosphere initially admitted isordinarily regulated to minimum ig.- nition temperatures in the range of500 to 1000 F.. depending on the type of catalyst, the nature oi' thecatalytic conversion it has promoted and the maximum temperaturesdesired in reactivation. In general, the service orconversiontemperature level will determine the reactivation temperature level fora catalyst.` For example, catalysts used in reactions conducted attemperatures of 900 to 1300 F. may bereactivated at temperatures withinthat range or only slightly hi'gher while catalysts used at temperaturesof 600 to 900 E. are reactivated at substantially `the same temperaturesbut not greatly' exceeding 1200 F. In either case, the temperature atthe beginning of the reactivation will be within the content of thecombustion aflcrded by my p rocess flow and eventually reaches ,the endof the catalyst bed. This terminates the nrst phase of reactivation. Thesecond phase. includes the ccmbustion of carbonaceous material mostlybeneath the surfacey of the catalyst granules, and higher oxygenconcentrations inthe combustion atmospheresere permissible and necessaryto rapidly complete the reactivation. Inv this phase the weight ofcarbonaceous material removed is relaslower'.

at various points within the catalyst mass or by time measurements oncethe time periods of the successive operations have been established fora given operation. The time required for the actual combustion ofcarbonaceous material will depend on the weight o! carbon on thecatalyst, the type of catalyst and catalyst 'vessels 4and other yfactorsinvolving the maximum desired temperatures during reactivation.. In-anycase, adjustv ment of my process toi any existing or desired the maximumpermissible temperatures are not I exceeded.

In most cases, catalyst bed temperatures durlng reactivation will notexceed 1200 to 1400* F., and only inexceptional instances willtemperatures above 1400 F.'be tolerated without incurring catalystdeterioration. On the other hand,

set of conditions involvfs only proper control of the volume oi' .theindicated gas streams being y mixed at a single point in the system.

At the completion of the reactivating combustion which may be judged bythe temperatures of the eiu'ent combustion atmosphere or of the catalystbedor by any conventional means, the iiow of oxygen-containingrgas isdiscontinued.

` and the catalyst is again purged with substantialreactivation is oftentoo slow'an'd involves the handling oi excessive volumes of combustionat'- mosphere when temperatures below about 500 to 700". F. aremaintained.

/Pressure's in my process are moderate superatmospheric pressures whichmay range from values at the blower discharge just suicient to overcomethe total pressure drop in the System 'to higher values of 150 poundsgauge or more maintainedV by pressureregulators on the eiuent gas lines.In some cases, higher pressures arey beneiicial in shortening the finalstages of reactivation;

"The reactivating combustion may be divided intoA two phases accordingto the potentialrate of combustion. The rst or rapid phase includes theperiod required for removal of. the surface coating' of carbonaceousmaterial from the cat. alyst granules. In'this period the oxygen con--`tent of the combustion must be very low, gener'-V ally of the order of0,5 to about 3 volume per cent to prevent excessive temperatures atthe-combustion front or zone of intense oxidation. This zone is thatAportion of the catalyst bed in which previously mentioned Reaction (l)isA occurring, involving the oxygen in the vcombustion atmosphere,andthe temperature of this zoner is gov- `erned bythe concentration oroxygen. and adjacent areas are'also the sectors oi? the catalyst bed inwhich gasification or carbon by vreaction with carbon dioxide and/orsteam occurs. l The gas passing through the combustion front is saisedin temperature with the result that the entire bed is moreor lessgradually heated .to

a level which permits secondary reactions throughout the mass. Y In myprocess the combustionvfront proceeds uniformly in. the direction ofreactivating gas This zone ly oxygen-free gasto prepare said 'catalystfor Y further conversion service. This n nal purge may be of relativelybrief duration, and the temperature of the purge ga's may beregulated ifdesired to bring the catalyst bed to approximately conversionconditions. rIhus, `ii? the reactivation is completed at say F. below orabove conversion temperature, the purge gasmay be utilized to raise orlower the catalyst temperature/to the desired range. In thise'case,the.catalyst may be -placed on stream by introducing the hydrocarbonreactants and stoppingtheow of purge gas.-

Such expedients are of value in conversions such' as catalytic crackingand the like wherein the complete cycle of operationswith'aunitofcatalyst may not be longer thanfrom one or less to labout sixhours. l

The operation of the pressure combustion chamber as a source ofsubstantially oxygen-free gas requires a'minimum of regulating control.

The oxygencontent of the stack gas delivered to the chamber isessentially constant. and the quantity of -iuel gas required to combinethe oxy- 'gen present in a constant volume 0L said stack gas is thusfixed. They combustion temperature produced by stackgas containing about10 Vol urne per cent of Voxygen is usually in the range of 2300 to 2500and this range promotes complete oxidation of the fuel to carbondioxide,

. gas containing maximum concentrations of carbon dioxidesubstantially'ireeof oxygen and carbon monoxide. In this respect,combustion is more complete than when fuel gas is burned according `to 1theoretical -airrequirements in' air alone or in air diluted by steam. I

Since the `waste-heat boiler utilizes the excess oi' sensible heat .orthe hot effluent gas from the catalyst chambers, a large portion or thesteam and power requirements is supplied by waste productsI of theprocess. The periods onmaximum steam requirement correspond ratherclose-v ly to the periods of maximum steam production since the largestyolume of substantially oxygen.-a

free gas is supplied to the catalyst duringthe' initial combustionperiod when the temperature of the eiliuent gas is at a maximum.Conversely, 4, the periods of minimum steam requirements con respond tothe periods of minimum steam production. for starting operations may besupplied as shown from an external source or may be generated in Ytherwaste-heatboiler by the auxiliary,comlius-1 tion of-fuelgas and airtherein or in the combustion chamber if desired..

The following specic examples will serve to illustrate applications o imy process to the reac tivation 'of catalysts used in specic conversionswhich diier greatly in respect to both conversion and reactivationconditions. Inasmuch as said examples are included toindicate theexibility and operating advantagesof my-process, no limitation isimpliedthereby.

Emample I Acatalytic gas-oil cracking operation was conducted with a.silica-alumina type catalyst under conditions such that theconversion-reactivation cycle was six hours. Of this cycle, the conver=sion period was two hours during which carbon deposition amounted toapproximately 2 per centby weight o the gas-oil charge. Three catalystchambers were employed in the operation, and the reactivation equipmentwas substantially the same as shown in Figure 2 except that gasmixingmanifolds were provided for the individual chambers.

After the catalyst'intherst chamber com pleted 2 hours or conversion,the now of' hydro-a carbon reactants was switched to the second chamber.The pressure on said rst chamber was released and'substantiallyoxygen-free gas delivered from the pressure-combustion chamber Excesssteam'requirements and steam assetto vation, with the third chamberbeing put on stream. The sequence of reactivation operations thusover-lapped With the initial purge and ini-A tial combustion period ofsaid second chamber occurring simultaneously with the ilnalcombustionperiod and nal purge or said ilrst chamber. By this scheme ofoperation the volume requirements for each of. the gas streams used inthe sequence of reactivating steps remained essen- ;tially constant.

Example II A bauxite catalyst used in the desulfurization oicrackedgasoline vapors at 750 F. was reat about 2400 F. and cooled toabout 050 F..

was introduced for the initial purge gas. The iiow of purge gas andhydrocarbon vapors was directed to a scrubber wherein the hydrocarbonsWere separated. n V

The initial purge was complete after 30 'i s utes, and with the catalystat approximately 950 F., the combustion was initiated by introducing amixture of stack gas with sufilcienf. substan tially oxygen-free gas toproduce an oxygen conn tent of about 2 volume per cent.' This initialmixture was20 per cent of stack' aaa and 't0 percent substantiallyoxygen-free sas, and was prepared by mixing 80% Oxygen-free gas from thepressure, combustion chamber with 20% cooled stack gas containing about10% oxygen to produce a. mixture 'temperature or about After a period o'1.5 hours, the initial combustion4 phase was complete with the maximumtemperature not substantially exceeding 1100"- 1200 F. and thetemperatures of the catalyst mass showed that the combustion front hadtrav ersed the bed. At this point, the oxygen content of the comlmstionatmosphere was raised to about activated. after 12 hours on stream.extended period of service, dual catalyst chambers of relatively largecross-section were providedand the reactivation was completed ih aboutl9 hours. The catalyst to be reactivated was-purged free -of gasolinevapors by means of'a`mixture of substantially oxygen-free ,gas prepared.as in 'the foregoing and steam,at a

.temperature of about "100I F. The purged catalyst was then yreactivatedfor a.' period or 7 hours with a combustion atmosphere composed of stackgas and said Asubstantially oxygen-free gas and steam entering thechamber at about 850 F. During reactivation', the oxygen content of thecombustion atmosphere was gradually increased adm 2.5 per cent to 1o percent', with the erst increase coming after 4 hours. Maximum temperatures-withinv the catalyst bed did not substantially exceed 1400 F. at anyperiod and during the last 2 hours of the 9 hour period the inlettemperature oi the combustion atmosphere was raised to 900 F. Thereactivation was completed in 9 hours, and the chamber was purged' againwith substantially oxygen-free gas and steam at a temperature of about'150 F. to eliminateoxygen.

My invention is not limited to the reactivation of any particular typeof catalyst nor to any specic conversion in which catalysts aredeactivated by the deposition of carbonaceous deposits. In generaL-thecatalysts to be reactivated according to the terms of the foregoingdisclosure are those which are restored to a suitable activity under'the specined controlled conditions' but which are susceptible todeterioration il.' the said specified conditions are exceeded duringreactivation treatment. Examples ot such materials are the variouscontact catalysts classified as clay-type and mineral ore materials andnatural or synthetic metal oxides including the difiicultly reducibleoxides alone or' in mixtures with each other and/or promoted with othermetals or metal salts. Specic examples are bauxite and bauxiteimpregnated with c mium.

zirconium. and other oxides used in (cracking.`

dehydrogenation; aromatization and desulrurization conversions andcomposite catalystsl prepared from-silicon and vated silicates.

With this aluminum oxides and'actiasaasso The term "stack gas and "spentcombustion gas" as employed in the foregoing disclosure are intended todesignate the gases produced by the combustion of fuels with moderateamounts of excess air according to conventional procedures known to theart.' Such gases ordinarily com prise carbon dioxide, nitrogen, oxygenand water vapor with the relative. amounts of' these and other minorcomponents varying according to the type of fuel and the eiiiciency of'the combustion operation. y

The term "moisture as used in certain of the appended claims includeswater in the form of either liquid water or steam. A

Having thus described my invention, I claim:

' l. A method of regenerating a catalyst of reduced activity by removingcombustiblel deposits from the catalyst which comprises burning fuel inan atmosphere of an oxygen-containing stack gas, the latter containing asubstantial amount but not over 10 ',volume per cent of oxygen andprepared by the combustion of fuel with a limited amount of excess air,the proportions of said fuel and said stack gas being so adjusted toproduce a substantially oxygen-free and carbon monoxidefree gas, mixingthe resultant substantially oxygen-free and carbon monoxide-free gaswith an oxygen-containing gas to form a regenerating gaseous mixturehaving an oxygen content of less than' 10% by volume, and introducingAsaid mixture into contact with the catalyst to regenerate the catalystby removal of combustible deposits from thecatalyst. y

2. A method of regenerating a catalyst of reduced activity byremovingcombustible deposits from thercatalyst which comprises burning fuel inan. atmosphere of stack gas, the latter containing a substantial amountbut not over 10 volume per cent of oxygen 'and prepared by thecombustion of fuel with a limited amount. of excess air, the proportionof said fuel and said stack gas being so adjusted to producesubstantially oxygen-free and carbon monoxide-freegas,

mixing the resultant substantially oxygen-free andi carbon monoxide-freegas with controlled cunts of said stack gas to form a regeneratinggaseous mixture having a controlled oxygen content of less than 10% byvolume, introducing the said mixture into contact with the catalyst toregenerate the catalyst by removal of combustible deposits from thecatalyst, and adding moisture to the'regenerating gaseous mixture tolimit the temperature of the regeneration below a predeterminedmaximum.,

3. lA method ofmaking a gas suitable for regenerating a catalyst ofreduced activity by removing combustibile deposits from the catalystwhich comprises burning fuel in an atmosphere of stack gas, the lattercontaining a substantial amount but not over 10 volume per cent ofoxygen and prepared by the combustion of fuel with a limited amount ofexcess air, to produce a substantially oxygen free and carbonmonoxidefree gas, and mixing the resultant substantially oxygen-free andcarbon monoxide-free gas with air to form a mixture of combustion4products and oxygen having an oxygen content of less than 10% byvolume.

a. In a process for the reactivation of solid contact catalysts employedin the conversion of hydrocarbons, the activity of which has beensubstantially reduced by the deposition of oxidizable carbonaceousmaterial thereon, which comprises passing a portion of a gas intocontact with the catalyst to purge the catalyst of hydrocarbon vapors,mixing another portion of said gas with'oxygen-containing combustionproducts -to produce a mixture of suitablereduced oxygen content, andpassing said mixture into contact with said catalyst to effect removalof the carbonaceous material by combustion and gasification of saidmaterial, the improvement which comprises generating said gas by burningfuel gas in an atmosphere of combustion products having a substantialcontent but not over 10 volume per cent of oxygen, the proportions ofsaid fuel and said combustion products being so adju'sted to produce agas containing carbon dioxide and substantially free of oxygen andcarbon monoxide.

JESSE A. GUYER.

cmrrreare or conmcron.

Patent No 2,5146 75.0

It is hereby certified that error appears 1n the printed specifi ot theabove mmbered patent' requiring correction as follows; Page 5, second'calm; 13u52, foraine rend #eline-m'. A =-exte; page 5, eccomi co1, lne7for .-ahosph I for "mise" read thie; page 7, f'rst column, line .l andthat the seid Letters Patent should .be

phare-5 V11m El..

Apr-11 18, 191th., y

Jesse-moms;

reed with this correction 'therein met the s'emelmay conform to therecord of the casein the-Patent Offices signed jam seared this 29th dayer ,august-p (Seal)` .D.- 191th. Y

Leslie Frazer Actng'Conmii'ssoner of Patents.

cation line 61|., for exists read eresa reed --etmoscnnnromn on comoon.

Patent No.4 2,5155750. April 18, 19h11.

.mssx1..oum;

It is hereby certifiedl that error appenrs 1n the printed specificationof the above numbered. patent requiring correction follows: Page 3,second' column', 11m 52, forine rend 11ne: line 611, for exists readexits-g pogo 5, econrl` column, line 7, for "vanospheros reed--atmoaphoto-g I Line 13.7,.ror 'v'thise" reid -thil; page 7, firstcolumn, line 1, for "tu-n' rnd tomar-- qnd mn: the 1d Lettera usentmould b,

I read vdth this correction 'therein that 'the namens; conform to therecord of the case 1n hepatent office. l Q

signed'am alga this 29th day of August, 1.11.1191111.

n v Leslie Frazer (Seal) ActingC-ommi'ssioner of Patents.

